Unpack theme data from extensions off of UI thread.

chrome/browser/ui/extensions/extension_install_ui_default.h

Index: chrome/browser/ui/extensions/extension_install_ui_default.h
diff --git a/chrome/browser/ui/extensions/extension_install_ui_default.h b/chrome/browser/ui/extensions/extension_install_ui_default.h
index 32d40e123676be1b4487ee52c7ff00a42fb15990..2586f2e9c7bdb2d701fae2ec6bf94f510dd520f5 100644
--- a/chrome/browser/ui/extensions/extension_install_ui_default.h
+++ b/chrome/browser/ui/extensions/extension_install_ui_default.h
@@ -35,10 +35,6 @@ class ExtensionInstallUIDefault : public extensions::ExtensionInstallUI {
   // Whether or not to show the default UI after completing the installation.
   bool skip_post_install_ui_;
 
-  // Used to undo theme installation.
-  std::string previous_theme_id_;
-  bool previous_using_system_theme_;
-
   // Whether to show an installed bubble on app install, or use the default
   // action of opening a new tab page.
   bool use_app_installed_bubble_;